Compressor stator assembly



July 8, 1958 H. A. ECKENFELS ET AL 2,842,305

COMPRESSOR STATOR ASSEMBLY Filed NOV. l, 1955 United St COMPRESSOR sTAron ASSEMBLY Application November 1, 1955, Serial No. 544,172

1 Claim. (Cl. 230-114) This invention relates to stator vanes in an axial dow compressor for a gas turbine engine or lthe like, and, in particular, to a means for varying the position of the stator vanes in an axial flow compressor.

Wherever high pressure ratio compressors of the axial flow type are used, aerodynamic stall conditions exist at some periods of acceleration when going from zero speed to maximum speed. lt has been found that the higher the pressure ratio, the more pronounced the stall conditions become. This stall condition exists as a result of the flow'failing to match the aerodynamic design of the 'blade itself. ln other words, the angle of attack is not in the proper relationship to the flow. Also, it is generally desirable to construct the structural members of the compressor of light material to keep the engine as light as possible. However, the stall conditions create vibrations which will tend to destroy these various light weight parts. By keeping the stall conditions to a minimum and thereby eliminating a large portion of the vibrations, the parts that go to make up the compressor can be constructed of lighter material. Therefore, in order to correct for stall conditions, it is a general object of this invention to vary the posi-tion of the stator vanes of an axial ow lcompressor 'by changing the angle of attack to. meet the particular flow condition over a wide range of operating conditions.

In order to make the stator blade of an axial flow cornpressor rotatable about its longitudinal axis, the base of each of theyblades isk actuated by a lever which in turn is actuated by a circumferential band extending labout the circumference ofthe compressor. The actuator band tends to move in an arc of a circle whereas the lever tends to pivot in a planetangential to this arc of a circle. Therefore, a problem arises as to how to connect the actuator band and lever to accommodate the dilferent relative movements without creating binding therebetween. It is therefore another object of this invention to provide a connection between the actuator band and lever which will permit the actuator band to -move in an arc of a circle and the lever to be pivoted in a plane tangential to the arc of a circle without resultant binding.

Although it is desirable to vary the angles of attack of stator blades in an axial flow compressor, it is a dicult problem to obtain simplicity of design and to eliminate heavy and cumbersome structures while still retaining the close dimensions required in accomplishing the reliability and accuracy needed in the operation of the device. Also tight connections between the parts are required so as to withstand the high vibrations encountered in this type of engine. It is therefore still another object of this invention to provide a mechanism for varying the stages of stator vanes in an axial flow compressor which is of simple and light weight construction and still providing a tight connection between the moving parts so as to be capable of withstanding the vibra-tory forces which tend to destroy the parts if loosely connected.

In prior art mechanisms for adjusting the stator vanes of an axial flow compressor, the parts extend outwardly from the casing so as to result in an overall increase in diameter of the engine.` The increase in diameter is `a detriment to the operation of the engine. Therefore, by using a linkage mechanism which closely surrounds the compressor casing to maintain the overall diameter 'at a minimum, assembly and disassembly of connecting parts becomes extremely difficult. This diiculty results since the parts are not readily accessible from both sides. Therefore, it is still a further object of this invention to provide a pin and clip means which is readily `accessible from one `side which permits ease of assembly and disassembly.

These and other objects will become more apparent when read in the light of the accompanying specification and drawing, and, wherein like parts are designated by the same numbers, and, wherein the specific terms used for the individual parts are intended to be as generic in their application as the prior art will permit, and wherein:

Fig. 1 is a sideview of a turbojet engine showing the compressor having a variable stator mechanism,

Fig. 2 is a cross-sectional View `taken lthrough the casing of a compressor showing the base of the stator vane and part of the actuating mechanism,

Fig. 3 is a cross-sectional view taken on lines 3 3 of Fig. 2 showing the connection between the Vactuator band and the lever arm,

Fig. 4 is a cross-sectional viewl taken on lines 4 4 of Fig. 3 showing the construction of the connection between the lever arm and actuator band.

Briey stated and in accordance with one aspect ofthe invention a variable stator mechanism for an axial flow compressor is provided in which an actuator ring and lever arm are tightly connected and are free to move without binding even though they rotate in different planes.

Referring to the drawings, the numeral lit generally designates a jet engine having a compressor section 12, a combustion section lli, a turbine section 16, tailpipe 18 and an exhaust nozzle 20. Referring to Fig. 2, the cornpressor section 12 is provided with a compressor casing y2 provided with vane basel openings 24.. Eachy Vane base opening 24 is counterbored or the like to, forma at bearing seat 'as shown at 26. The vanevbase opening and the at bearing seat 26 is lined` with` a bearing material such as polytetrauoroethylene or the like. A stator vane or the like is shown at 3 0 and is provided-with, a vane base 32 provided with a flat bearing seat, 34, which is adapted` to be supported in the vane base openingv 24 and on the flat bearing seatZo.y The statory vanevbase 32 is also provided with an integral stud 36 terminating in a threaded end.` A cap 38 or the like is mounted on the vane base 32 in order to hold the stator vane 30 on the compressor casing. Also the stator vane base is provided with a tang 40 extending upwardly from and integral with the vane base. A lever 42 is mounted on the stator vane base and is provided with a recessed portion 44 having a stud opening 46 land a tang opening 4S. In order to secure the lever to the vane base the lever is positioned over the stud 36 with the opening 48 positioned over the tang 40 and the stud opening 46 positioned over the stud 36 and secured by a nut or the like 5t). The nut also holds the lever 42 against the cap 38. By fixing the lever 42 to the stator vane 30, they rotate in unison.

Referring to Fig. 1, a pneumatic, hydraulic, or electrical actuator is shown at 52. lt is provided with an actuating rod 54 and an actuating arm 56. A plurality of slots 58, one for each stage of stator vanes is provided in the actuating arm, each at different angles, so las to provide different movements to each of the stages of stator vanes. Such an arrangement has been shown land described in application Serial Number 509,307, tiled May 18, 1955, assigned to the same assignee as the assignee of this application. Although this type of an actuating means has been described, other types may be used in connection with this invention. The actuating arm 56, slot S8, and pin 59, slidably mounted in the slot, cooperate to actuate actuating bands 60, 'there being one for each stage of stator vanes. The pin 59 is xed to the actuator band 60. The actuating band is in the -form of a circumferential channel type ring extending around the compressor casing. An opening 62 extends through the legs 61 and 63 of the channel type ring or actuator. A pin 64 is provided which extends through the opening 62. In order to provide easy access to the pin lfor speedy removal and insertion, the pin 64 is provided with a head 66. A fork clip is shown at 70, having a fork 71 at one end adapted to frictionally engage the pin 64 on the inside` of the channel ring and a fork 73 on the other end adapted to extend over the head 66 of the pin frictionally engaging the pin. A cotter pin is shown at 72 for se-curing the pin in position thereby locking it with respect to the actuating ring. This arrangement holds the pin in the ring so as to provide a locking means therefor, yet making it relatively accessible and removable.

Referring to Fig. 4, the lever 42 contains an opening 74. The opening is adapted to receive a spherical self-aligning bearing generally shown at 76. The bearing comprises an outer race 75 which can be secured in the opening "I4 by staking or the like. The spherical bearing also contains a socket 78 and a ball 80 through which an opening 82 extends. The pin 64 extends through the opening 82. In order to secure the lever to the ring, the lever arm 42 with bearing 76 is positioned within the channel type actuating ring, so as to align the opening 62 in the ring with the opening 82 in the ball 80. The pin 64 is then slipped through the ring 60 in the opening 62 and through the opening 82 in the ball 80. When this is done, the fork clip 70 is slipped over the head 66 and under the channel portion 61 as seen in Fig. 2. The pin is secured in place by inserting the cotter pin 72 in the end of the pin. The ball 80 is spaced from the legs 61 and 63 to permit the ball to lslide up and down the pin 64 to compensate for the change in distance between the lever arms 42 and actuator ring 63.

Generally controls are used which are responsive to various parameters such as speed, temperature and pressure, which receive a signal indicating that the position of the stator vanes should be changed for the particular running condition. When a change in speed, temperature or pressure is sensed to Warrant rotating the stator vanes, the controls transmit the signal to the actuator S2 which transmits linear motion to the actuator arm 56, which in turn transmits rotary motion to the actuator ring 60. The rotary motion of the ring transmits rotary motion to the lever 42 for rotating the stator vanes. It is noted that the actuator ring moves in an are of a circle. Also, it is noted that the lever rotates about a point transversely of the compressor and in a plane tangential to the arc of a circle in which the actuating ring rotates. This being the case there is a tendency for the actuator ring and the lever to bind and twist with respect to each other and to separate. ,In order to permit the different relative motions and prevent binding or the like of the connection between the lever and the actuator ring, the spherical self-aligning bearing 76 is provided. The lever being mounted on the socket portion 78 of the bearing tends to rotate about the `ball 80. This will permit the pin 64 to retain its position in the actuator ring 60 without binding or twisting while still permitting the lever arms to rotate in the plane which is tangential to the movement of the arc of the circle of the actuator ring. Also, since the actuator rings 60 are supported by the levers 42, they move axially of the compressor when the levers rotate.

Therefore, a novel arrangement has been provided for transmitting motion between the actuator ring and the lever arm by the use of the spherical self-aligning bearing construction. This eliminates twisting and binding between the parts to resist the vibratory forces which would destroy the connection if the connection were loose.

While the particular embodiment of the invention has been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention and it is intended to cover in the appended claim all such changes and modifications that come within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

An axial flow compressor comprising a casing, a plurality of stages of opening in said casing, a stator blade rotatably supported in each of said openings, a lever arm secured to each of said stator blades, each of said lever g arms having a. ball and socket bearing in one end thereof,

an actuating ring secured to each stage of lever arms by pins secured thereto, said pin extending through the ball and socket bearing and having a head thereon, and a fork clip extending about said actuating ring and over said head to retain said pin in position, and means for actuating said actuating ring to transmit rotary motion to said stator vanes.

References Cited in the le of this patent UNITED STATES PATENTS 2,371,706 Planiol Mar. 20, 1945 FOREIGN PATENTS 500,965 Great Britain Feb. 20, 1939 1,080,166 France May 26, 1954 

